1. Immobilization stress does not increase regional cerebral blood flow in conscious rats, indicating that cerebral metabolism, to which blood flow is coupled, is insensitive to increased circulating catecholamines. The blood-brain barrier may contribute to this insensitivity. 2. Glucose utilization (GU) tends to increase in sympathetic ganglia between 12 and 24 months of age in the Fischer-344 rat. The increase is statistically significant in the superior cervical ganglion, and may be related to increased circulating norepinephrine. 3. Paraganglia, which contain catecholamines and are extra-adrenal chromaffin tissue, degenerate after birth in the rat but reappear between 24 and 33-months of age, and contain high concentrations of catecholamines. 4. Catecholamine fluorescence mapped from single neuron perikarya decreased with age in certain peripheral sympathetic ganglia as well as in certain brain regions which contain catecholamine-containing neurons.